What is a rear radar blocker?
What is a high temperature absorber?
J-20 5th Gen Fighter Thread VIII
- Thread starter Blitzo
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What is a high temperature absorber?
F-22 and F-35 have afterburner diffuser, part which inject fuel for afterburner shaped in special manner that will block view to its turbine blade
This is example for F-22.
Notice that the turbine blade are not visible. You can compare it with conventional AL-31 and WS-10
High temperature radar absorber is of course radar absorbent material that is designed to operate in high temp. Given that the diffuser or radar blocker is going to get hot air directly from the turbine, typical radar absorbent paint will not work as they would get burned or lost its absorbing properties due to the heat. Therefore special absorbing material, maybe based on carbide is required
It is not clear that the existing WS-10C on the J-20 does not have this. Regardless, the rear turbine is visible from a far narrower angle than the nozzle and so RCS reduction for the nozzle is meaningful regardless of the rear turbine signature.
That is good to know info, but I'm not sure how effective these diffusers would be considering the amount of scattering and bouncing around and the fact that nozzle coatings might shave off due to excessive heat and supersonic jet velocity. The converging diverging nozzle would definitely provide some help in hiding parts of the blades, but regardless of these benefits, they aren't enough to render flat nozzles irrelevant. Adding a flat nozzle to the equation would still improve LO regardless.
I made a post here a short while back outlining some of the benefits of flat nozzles over axisymmetric nozzles.
J-XY/J-35 carrier-borne fighter thread
though that's as much a fault of the bad original Chinese descriptions. Spend five minutes staring at the strake comment wondering what he meant. Sigh. Right. To clarify, what about the tailsting being extended relative to the fuselage gives the impression that it may have any relation to the...
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It doesn’t. Yang Wei revealed that J-20’s rear aspect RCS is larger than that of the F-22 during his presentation.
Rear aspect RCS is not the same as nozzle cavity RCS.
Is this addressed with the WS-15 or is it an inherent thing with round vs flat nozzles?
He said due to weakness in engine they had to go with round nozzles. He didn’t talk about rear engine block but it is obvious from high def photos we have of the inside of the nozzles that WS-10C doesn’t have them.
Which photo shows the nozzle cavity?
Not directly. He implied it. The phrasing was along the line of "rear RCS is not very relevant because that is not where you want to face the enemy". This suggest they have considered optimization there, but decided it unneeded.